<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>速度动画</title>
<style>
body,div,span{
	margin:0;
	padding:0;
	}
#div1{
	width:200px;
	height:200px;
	background:red;
	filter:alpha(opacity 30);
	opacity:0.3;
	}
</style>
<script>
window.onload = function(){
	var oDiv = document.getElementById('div1');
	oDiv.onmouseover = function(){
		startMove(100);
		}
	oDiv.onmouseout = function(){
		startMove(30);
		}
	var timer = null;
	var alpha = 30;
	function startMove(iTarget){
		var oDiv = document.getElementById('div1');
		  clearInterval(timer);
		  timer = setInterval(function(){
			  var speed = 0;
			  if(alpha>iTarget){
				  speed = -10;
				  }
			  else{
				  speed = 10;
				  }	  
			  if(alpha == iTarget){
				  clearInterval(timer)
				  }
			  else{
				  alpha+=speed;
				  oDiv.style.filter = 'alpha(opacity:'+alpha+')';
				  oDiv.style.opacity = alpha/100;
				  }	  
			  },30);
		}		
	}
</script>
</head>

<body>
<div id="div1">
</div> 
</body>
</html>
